From 404e003cf1065fea0a9aeebe62b9392f8f9102e4 Mon Sep 17 00:00:00 2001
From: Dmitry Stogov <dmitry@zend.com>
Date: Wed, 9 Dec 2015 05:16:30 +0300
Subject: [PATCH] Delete empty live-ranges

---
 ext/opcache/Optimizer/block_pass.c  | 35 ++++++++++++++++++++---------
 ext/opcache/Optimizer/zend_cfg.c    | 14 ++++++++++++
 sapi/phpdbg/tests/stepping_001.phpt |  4 ++--
 3 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/ext/opcache/Optimizer/block_pass.c b/ext/opcache/Optimizer/block_pass.c
index d2695c6c4b..91a86f05f1 100644
--- a/ext/opcache/Optimizer/block_pass.c
+++ b/ext/opcache/Optimizer/block_pass.c
@@ -778,6 +778,9 @@ static void assemble_code_blocks(zend_cfg *cfg, zend_op_array *op_array)
 					MAKE_NOP(opline);
 					b->end--;
 				}
+			} else if (b->start == b->end && opline->opcode == ZEND_NOP) {
+				/* skip empty block */
+				b->end--;
 			}
 			len += b->end - b->start + 1;
 		} else if (b->start <= b->end) {
@@ -801,14 +804,15 @@ static void assemble_code_blocks(zend_cfg *cfg, zend_op_array *op_array)
 	/* Copy code of reachable blocks into a single buffer */
 	for (b = blocks; b < end; b++) {
 		if (b->flags & ZEND_BB_REACHABLE) {
-			uint32_t n;
-
-			ZEND_ASSERT(b->start <= b->end);
-			n = b->end - b->start + 1;
-			memcpy(opline, op_array->opcodes + b->start, n * sizeof(zend_op));
-			b->start = opline - new_opcodes;
-			b->end = opline - new_opcodes + n - 1;
-			opline += n;
+			if (b->start <= b->end) {
+				uint32_t n = b->end - b->start + 1;
+				memcpy(opline, op_array->opcodes + b->start, n * sizeof(zend_op));
+				b->start = opline - new_opcodes;
+				b->end = opline - new_opcodes + n - 1;
+				opline += n;
+			} else {
+				b->start = b->end = opline - new_opcodes;
+			}
 		}
 	}
 
@@ -913,11 +917,22 @@ static void assemble_code_blocks(zend_cfg *cfg, zend_op_array *op_array)
 		map = (uint32_t *)do_alloca(sizeof(uint32_t) * op_array->last_live_range, use_heap);
 
 		for (i = 0, j = 0; i < op_array->last_live_range; i++) {
+			if (op_array->live_range[i].var == (uint32_t)-1) {
+				/* this live range already removed */
+				continue;
+			}
 			if (!(blocks[cfg->map[op_array->live_range[i].start]].flags & ZEND_BB_REACHABLE)) {
 				ZEND_ASSERT(!(blocks[cfg->map[op_array->live_range[i].end]].flags & ZEND_BB_REACHABLE));
 			} else {
-				op_array->live_range[i].start = blocks[cfg->map[op_array->live_range[i].start]].start;
-				op_array->live_range[i].end = blocks[cfg->map[op_array->live_range[i].end]].start;
+				uint32_t start_op = blocks[cfg->map[op_array->live_range[i].start]].start;
+				uint32_t end_op = blocks[cfg->map[op_array->live_range[i].end]].start;
+
+				if (start_op == end_op) {
+					/* skip empty live range */
+					continue;
+				}
+				op_array->live_range[i].start = start_op;
+				op_array->live_range[i].end = end_op;
 				map[i] = j;
 				if (i != j) {
 					op_array->live_range[j]  = op_array->live_range[i];
diff --git a/ext/opcache/Optimizer/zend_cfg.c b/ext/opcache/Optimizer/zend_cfg.c
index 374bf25e48..77e5dc1942 100644
--- a/ext/opcache/Optimizer/zend_cfg.c
+++ b/ext/opcache/Optimizer/zend_cfg.c
@@ -90,8 +90,22 @@ static void zend_mark_reachable_blocks(zend_op_array *op_array, zend_cfg *cfg, i
 
 			/* Add brk/cont paths */
 			for (j = 0; j < op_array->last_live_range; j++) {
+				if (op_array->live_range[j].var == (uint32_t)-1) {
+					/* this live range already removed */
+					continue;
+				}
 				b = blocks + block_map[op_array->live_range[j].start];
 				if (b->flags & ZEND_BB_REACHABLE) {
+					while (op_array->opcodes[b->start].opcode == ZEND_NOP && b->start != b->end) {
+						b->start++;
+					}
+					if (op_array->opcodes[b->start].opcode == ZEND_NOP &&
+					    b->start == b->end &&
+					    b->successors[0] == block_map[op_array->live_range[j].end]) {
+						/* mark as removed (empty live range) */
+						op_array->live_range[j].var = (uint32_t)-1;
+						continue;
+					}
 					b->flags |= ZEND_BB_GEN_VAR;
 					b = blocks + block_map[op_array->live_range[j].end];
 					b->flags |= ZEND_BB_KILL_VAR;
diff --git a/sapi/phpdbg/tests/stepping_001.phpt b/sapi/phpdbg/tests/stepping_001.phpt
index 074eeb47fa..bec14d4487 100644
--- a/sapi/phpdbg/tests/stepping_001.phpt
+++ b/sapi/phpdbg/tests/stepping_001.phpt
@@ -32,14 +32,14 @@ prompt> [L10 %s ECHO                    "ok"
  00011: } finally {
  00012: 	echo " ... ok";
 prompt> ok
-[L10 %s FAST_CALL               J8                                        ~%d                   %s]
+[L10 %s FAST_CALL               J7                                        ~%d                   %s]
 [L12 %s ECHO                    " ... ok"                                                      %s]
 >00012: 	echo " ... ok";
  00013: }
  00014: 
 prompt>  ... ok
 [L12 %s FAST_RET                ~%d                                                             %s]
-[L10 %s JMP                     J10                                                            %s]
+[L10 %s JMP                     J9                                                             %s]
 >00010: 	echo "ok";
  00011: } finally {
  00012: 	echo " ... ok";
-- 
2.40.0